GB879747A - Improved gas turbine engine fuel system - Google Patents

Abstract

879,747. Fluid-pressure servomotor-control systems. ROLLS-ROYCE Ltd. June 15, 1960 [June 24, 1959], No. 21684/59. Addition to 850,477. Class 135. [Also in Group XXVI] In a gas-turbine engine fuel system means are provided for supplying fuel under pressure from a source thereof to a burner of the engine through a metering orifice, the size of the metering orifice being varied in accordance with engine speed also in accordance with the ratio of the outlet and intake pressures of a compressor of the engine. Temperature responsive means are provided for varying the size of the metering orifice in accordance with the temperature of a part of the engine; alternatively means are provided for over-riding the pressure responsive means if the outlet pressure exceeds a predetermined value. Means are also provided for metering the fuel flow to the burner in accordance with the pressure drop across the metering orifice. The apparatus shown comprises a chamber 17 formed by a series of ducts and connected to the compressor discharge pressure P 2 through restrictor 16 and to compressor inlet pressure P 1 through restrictor 15. The pressure within the chamber 17 is communicated through duct 13 to a pressure-sensitive device which is arranged to control the size of a metering orifice which controls fuel flow through the fuel system. The chamber 17 is formed with a duct 18, the outlet of which is controlled by a valve 21 the position of which is varied by means of a solenoid or motor 22 which operates in dependence on a signal received from a probe 23 which senses the temperature of the jet pipe of the engine or of the turbine exhaust gases flowing therethrough immediately downstream of the turbine or turbines of the engine. The chamber 17 is also formed with a duct 25 the outlet of which is controlled by a valve 26 the position of which is controlled by means of an evacuated capsule 28 disposed within a chamber 29 which is subjected to compressor discharge pressure P 2 by means of duct 30. A spring 31 is disposed within the capsule 28 to exert a pressure corresponding to the desired maximum of P 2 pressure. A valve 19 is disposed within the duct 18 to permit the duct to be closed in the event of failure of the temperature-sensing control device. The pressure within the chamber 17 when the valves 21, 26 are completely closed is P 1 F (P 2 /P 1 ). Opening of the valves 21, 26 will produce a reduction in the pressure within the chamber, the reduced pressure being communicated to the pressure-sensitive device controlling the fuel metering orifice.